OCCURRENCE OF PYLAIELLA VARIA IN SCOTLAND 105 



question ; but it seems desirable, for the sake of convenience, 

 that when two plants differ in habit and mode of growth 

 and development so much as do P. litoralis and P. varia, and 

 retain their characteristics in different countries, they should 

 be kept distinct, as, for example, is done in the Ruin, Salices, 

 and Hieracia, amongst Phanerogams. If Dr. Kuckuck's plan 

 were followed, there would be little reason for holding Ecto- 

 carpus distortus and E. Landsburgii distinct from E. toinen- 

 tosus, Lyngb. The plurilocular fruits borne on specimens of 

 E. Landsburgii sent me by Mr. D. Robertson of Cumbrae, 

 and those of E. distortus collected by myself at Fairlie in 

 Ayrshire, show so great a resemblance to those of Ecto- 

 carpus tomentosus that I see no reason why they should not 

 both be considered as sub-species of that plant, more especially 

 as the differences in ramification and in the size of the zoo- 

 sporangia are not greater than exist between P. litoralis and 

 P. varia. A careful search on the west coast of Scotland 

 would doubtless reveal an intermediate series of forms con- 

 necting the three plants E, tomentosus, E. distortus, and E. 

 Landsburgii. 



It may be noted in this relation that Dr. Kjellman 

 identifies the E. Landsburgii of Dickie, "Alg. Suth," i. p. 

 142, with Pylaidla varia. But it has not been shown that 

 Dickie correctly referred this plant to E. Landsburgii. Dr. 

 Kjellman says of the gametes of P. varia that they are un- 

 known ; but Dr Kuckuck describes both the unilocular and 

 plurilocular zoosporangia (gametes) of his P. litoralis, f. 

 varia. 



DESCRIPTION OF PLATE III. 



Fig. i. Pylaiella varia, Kjellm., from Cromarty Firth, 

 with unilocular sporangia. 



2. The same more highly magnified. 

 3. With plurilocular sporangia. 



,, 4. Ectocarpus Landsburgii from Cumbrae, with pluri- 

 locular sporangia. 



